1. Field of the Invention
The present invention relates to a drill grinder for grinding or sharpening a point of a drill held in a drill holder, by forcing the drill point onto a grinding wheel, and more particularly to a technique for improving the grinding accuracy.
2. Discussion of the Prior Art
Various types of drills are widely used in the art of cutting holes in a workpiece. Since the cutting edges at the point of such drills are subject to wear during service, it is necessary to recondition or sharpen the drill point by grinding. For this purpose, there is known a drill grinder which uses a holding device for removably holding a drill. In this type of drill grinder, the point of the drill held in the holding device is ground such that the drill point and a grinding wheel are forced against each other.
Generally, the drill holding device used in the drill grinder indicated above is adapted to hold a drill at its shank. This means a relatively large distance between the drill point to be ground, and the portion of the drill at which the drill is held or gripped by the holding device. Consequently, the drill tends to be easily elastically deformed due to a grinding force applied between the drill point and the grinding wheel during a grinding operation. Such elastic deformation of the drill causes radial displacement or offsetting of the drill point from the rotating axis of the drill, resulting in deteriorating the accuracy of grinding of the cutting edges at the point of the drill.